1. Field of Invention
The present invention relates to a crystal form of (S)-4-hydroxy-2-oxo-1-pyrrolidine acetamide, a preparing method and a use thereof.
2. Description of the Related Art
(S)-4-hydroxy-2-oxo-1-pyrrolidine acetamide is a levorotatory form of oxiracetam, also called commercially (S)-oxiracetam [hereinafter the (S)-oxiracetam]. The chemical structure of (S)-oxiracetam is shown below:

As reported, it is published that oxiracetam is a synthetic cyclic compound derivatives of γ-Amino-β-hydroxybutyric acid (GABOB) is one of the efficacious drugs for Alzheimer's Disease (AD), vascular dementia or the like, which can promote ATP in the brain and the synthesis of acetylcholine, and also enhance transmission of the nerve excitation, improve the retrograde amnesia resulting from lack of oxygen, enhance memory and strengthen learning ability. However, in clinical application, oxiracetam is not ideal for treatment of dementia because of the inefficacious and even antagonistic ingredients therein. It is found in our researches that the efficacy described above of (S)-oxiracetam is much better than that of racemic oxiracetam. Some patents disclose preparation methods of levo-oxiracetam, such like WO/2005115978, CN101367757. CN101367757 discloses a (s)-4-hydroxy-2-oxo-1-pyrrolidine acetamide, which comprises steps of:
(a) adding glycinamide HCl, and partial inorganic bases into alcohol solvent, controlling the pH value being 7.3±0.3, agitating with increasing the temperature and refluxing;
(b) after 2-hour refluxing, adding (S)-4-halo-3-hydroxybutyryl ester, and the surplus inorganic bases in batches at the same time to make the pH value of being ≦8.5 during reaction;
(c) refluxing and reacting after adding (S)-4-halo-3-hydroxybutyryl ester, filtering and concentrating after the reaction finished to obtain a crude product of (S)-4-hydroxy-2-oxo-1-pyrrolidine acetamide;
(d) dissolving the crude product in water and treating the solution with strongly acidic styrene type cation exchange resin as well as collecting products, treating the products with strongly basic styrene type cation exchange resin to neutralize the collected products;
(e) using ethanol to recrystallize the neutralized products, and using isopropanol or methanol/propanol solution to recrystallize the neutralized products again, than obtaining (S)-oxiracetam.
However, it is found that a variety of crystal forms of (S)-oxiracetam exist, depending upon different preparing methods or post-treatment.